David B. Buller PhD, Dallas R. English PhD, Mary Klein Buller MA, Jody Simmons , James A. Chamberlain PhD, Melanie Wakefield PhD, and Suzanne Dobbinson PhD
Objectives. To test whether shade sails will increase the use of passive recreation areas (PRAs).Methods. We conducted a stratified randomized pretest–posttest controlled design study in Melbourne, Australia, and Denver, Colorado, in 2010 to 2014. We randomized a sample of 144 public parks with 2 PRAs in full sun in a 1:3 ratio to treatment or control. Shade sails were built at 1 PRA per treatment park. The outcome was any use of the study PRA (n = 576 pretest and n = 576 posttest observations; 100% follow-up).Results. Compared with control PRAs (adjusted probability of use: pretest = 0.14, posttest = 0.17), use of treatment PRAs (pretest = 0.10, posttest = 0.32) was higher at posttest (odds ratio [OR] = 3.91; 95% confidence interval [CI] = 1.71, 8.94). Shade increased use of PRAs in Denver (control: pretest = 0.18, posttest = 0.19; treatment: pretest = 0.16, posttest = 0.47) more than Melbourne (control: pretest = 0.11, posttest = 0.14; shaded: pretest = 0.06, posttest = 0.19; OR = 2.98; 95% CI = 1.09, 8.14).Conclusions. Public investment in shade is warranted for skin cancer prevention and may be especially useful in the United States.
RESULTS:
Table 1 displays the characteristics of the parks and PRAs for the pretest and posttest observations by experimental condition and city. The most common amenities within the PRAs were benches and picnic tables; playgrounds were the most frequent amenity close to the PRAs. The PRAs were located in parks within diverse neighborhoods. Neighborhood characteristics were the same between experimental conditions. A total of 576 pretest observations and 576 posttest observations were performed at 144 PRAs (71 in Melbourne and 73 in Denver; Table 2). One park in Melbourne was eliminated after randomization because park renovations substantially altered PRA amenities during posttesting. An extra park was enrolled in Denver. The protocol resulted in observations occurring in proximity to the summer solstice (mean = 29 days from the solstice at pretest and mean = 50 days at posttest; differences were caused by delayed construction of some shade sails) and at midday (mean = 55 minutes from solar noon at pretest and 56 minutes at posttest; Table 2). Weather conditions were warm (mean = 26.2°C at pretest and 25.5°C at posttest), with some cloud cover for 71.6% of observations at pretest and 67.7% at posttest, but there was only slight or no wind for 69.1% of the observations at pretest and 71.1% at posttest. Differences between the cities were small, with weather appearing to be cooler, cloudier, and windier in Melbourne than in Denver during the observations. Randomization appeared successful because there were no statistically significant differences on neighborhood characteristics, setting features of the PRAs, or features of the observation periods between experimental conditions.
DISCUSSION:
Shade is an essential aspect of skin cancer prevention. Our results in this trial showed that building shade sails in public parks increased the likelihood that adults would choose to use shaded PRAs more than unshaded ones. Use of the unshaded comparison PRAs remained consistent from pretest to posttest in both conditions, further suggesting that it was the construction of shade that increased use of the study PRAs. Our findings from a prospective randomized comparison provided clear evidence for the potential of purpose-built shade sails using cloth that blocked at least 94% of UV exposure to minimize that exposure, which can damage the skin.Our findings provided stronger evidence for the impact of shade in sun protection interventions than did most past studies. Several interventions included shade, along with education on sun safety,22 but evaluations could not partition the effect of shade from other prevention practices.9 Along with our previous trial that found more adolescents used shaded than unshaded areas at school,9 individuals of all ages appeared to use purpose-built shade in outdoor public communal areas. Shade should be an effective community-based skin cancer prevention intervention because it does not rely on educating individuals or preplanning by them. To be most effective, purpose-built shade should (1) provide shade during the hours close to solar noon in summer when UV light is at its peak,23 and (2) create warm light-colored shade of a relatively large size.24
Nonetheless, the number of users during any observation period was small. Parks and their recreation areas might be used less consistently than school grounds. School grounds are moderate to small locations where a concentrated number of individuals (i.e., students and staff) are required to exist together every weekday during school terms. Public parks can be large and present many PRAs to users. Individuals who use parks may do so irregularly, and some may go to parks to get away from other people. The low overall use necessitated changing our outcome measure to probability of use, rather than total number of users. It also meant that during many 30-minute observation periods, no individuals were observed using the PRA and thus no individuals were being protected by the shade sails. Our school study also had many observation periods with no use of the recreation areas. Future research is needed to determine factors that influence use of shaded recreation areas. In our school study, warm temperatures and lunch tables in the recreation areas predicted more use.11 Warm temperatures might make shade attractive for maintaining comfortable body temperature. Shade might be best placed in areas where people naturally gather for passive activities such as community hubs, markets, performing arts sites, dining areas, and recreation spectator areas. Active recreation areas pose challenges for shade because (1) large areas such as courts and fields might be prohibitively expensive to shade, (2) some sports require locations with no overhead obstacles, and (3) the supports for shade sails might pose collision hazards and fall zones.Unexpectedly, most of the gains in use of the shaded PRAs occurred in Denver rather than Melbourne. We predicted, based on social-ecological models, that purpose-built shade would be more effective in a society with stronger sun safety norms created by Australia’s 25 years of community-wide, comprehensive sun safety efforts.17,25 Differences in weather conditions, setting, and neighborhood features between cities might have explained this contrary finding, but they were controlled in the analysis. One possibility was that because of sun safety awareness, Australians might spend less time outdoors during midday to reduce their UV exposure. Also, the parks in Melbourne were in suburban areas, where residents might have more residential yard space and thus less motivation to use parks. By contrast, several Denver parks were in the high-density urban core where residents might have used the parks more to compensate for a lack of yard space.26 However, we included use of the comparison PRA as a covariate to account for differences in park use, and by this measure, there might have been slightly more individuals in the parks at posttest in Melbourne than in Denver (but we did not adjust this measure for the number of other PRAs in the park, and it was not a count of actual park visitors). Because of sun safety efforts, there might be more existing purpose-built shade throughout Melbourne compared with Denver. Consequently, adding 1 more shade sail in a park might not have been seen as noteworthy by Australians in Melbourne, whereas the new shade sails might have been novel to individuals in Denver, causing them to notice and use them. There also might have been fewer existing shaded areas in the Denver than in the Melbourne parks, because Denver is in a more arid climate. We did not control for the amount of existing shade, so we could not directly test these explanations. It was also possible that apparently lower average temperatures in Melbourne than in Denver reduced use of shaded PRAs because they were uncomfortably cool. However, we controlled for temperature in the model, and the temperature was warm in Melbourne (24°C [75°F] on average). Despite this unexpected difference by city, our study provided further evidence that environmental features could influence skin cancer prevention behaviors. Similar evidence was provided by a study that showed that the density of tanning bed facilities affected indoor tanning by youths.27
The project was supported by a grant from the US National Cancer Institute (CA140367). M. Wakefield was supported by an Australian National Health and Medical Research Council Principal Research Fellowship. Gale Pacific Limited provided the shade cloth at no cost for the shade sails built in Melbourne, Australia.
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https://ajph.aphapublications.org/doi/full/10.2105/AJPH.2017.304071#_i6